Marcus, IA has a population of 1,146 and is the 14,315th largest city in the United States. The population density is 745 per sq mi which is 1265% higher than the Iowa average and 723% higher than the national average. The median age in Marcus is 53 which is approximately 39% higher than the Iowa average of 38. In Marcus, 71% of the population over 15 years of age are married, 97% speak English and 2% speak Spanish. 74% of Marcus residents were born in Iowa, 25% were born out of state, 1% were born outside of the United States and 0% were foreign born.